86900-29-0Relevant academic research and scientific papers
Synthesis of 7-hydroperoxycholesterol and its separation, identification, and quantification in cholesterol heated model systems
Nogueira, Gislaine C.,Costa, Bruna Z.,Crotti, Antonio E. M.,Bragagnolo, Neura
, p. 10226 - 10230 (2010)
7-Hydroperoxycholesterol is considered to be an intermediate compound of the cholesterol oxidation path as the first product formed when cholesterol is oxidized by triplet oxygen. However, there is a limitation on cholesterol mechanism studies because of the lack of 7-hydroperoxycholesterol analytical standard due to its low stability. To verify the formation of hydroperoxides in cholesterol model systems heated at 140, 180, and 220 °C, 7α-hydroperoxycholesterol was synthesized by cholesterol photooxidation followed by rearrangement at room temperature in chloroform. Its structure was confirmed on the basis of 13C NMR and mass spectra obtained by APCI-LC-MS. The synthesized compound was also used as standard for the quantification of 7-hydroperoxycholesterol as the sum of 7α-and 7β-hydroperoxycholesterol. The results demonstrated that 7-hydroperoxycholesterol is the first compound formed when the temperature is lower (140 °C). However, the concentration of the 7-hydroperoxycholesterol depends on the temperature and time of exposure: the higher the time, the higher the amount of 7-hydroperoxycholesterol at lower temperatures, and the lower the time, the lower the amount of 7-hydroperoxycholesterol at higher temperatures (180 and 220 °C). By the formation of 7-hydroperoxycholesterol, the known cholesterol oxidation mechanism in three phases (initiation, propagation, and termination) could be confirmed; once at lower temperatures, the stage of cholesterol oxidation is at initiation, at which hydroperoxide formation predominates.
Comparison of photo-oxidation reactions in batch and a new photosensitizer-immobilized microfluidic device
Lumley, Emily K.,Dyer, Charlotte E.,Pamme, Nicole,Boyle, Ross W.
supporting information, p. 5724 - 5727 (2013/01/15)
A glass microfluidic device has been functionalized with photoactive porphyrins for performing reactions which are mediated by singlet molecular oxygen. The resulting device was used to investigate the photochemical oxidation of cholesterol, α-terpinene, and citronellol under flow conditions, and the results were compared with similar batch reactions.
Cholesterol hydroperoxides generate singlet molecular oxygen [O 2(1Δg)]: Near-IR emission, 18O-labeled hydroperoxides, and mass spectrometry
Uemi, Miriam,Ronsein, Graziella E.,Prado, Fernanda M.,Motta, Flavia D.,Miyamoto, Sayuri,Medeiros, Marisa H. G.,Di Mascio, Paolo
experimental part, p. 887 - 895 (2012/04/11)
In mammalian membranes, cholesterol is concentrated in lipid rafts. The generation of cholesterol hydroperoxides (ChOOHs) and their decomposition products induces various types of cell damage. The decomposition of some organic hydroperoxides into peroxyl
Synthesis, characterization, and electrochemical studies of new π-Extended metalloporphyrins
Jimenez, Angel J.,Jeandon, Christophe,Gisselbrecht, Jean-Paul,Ruppert, Romain
supporting information; experimental part, p. 5725 - 5730 (2010/03/01)
A doubly fused porphyrin has been synthesized by two successive cyclization reactions. The first meso-phenyl group was fused, by an intramolecular Cadogan reaction leading to an enamine-functionalized porphyrin. After Vilsmeier-Haack formylation of the ni
Allylic oxidations catalyzed by dirhodium caprolactamate via aqueous tert-butyl hydroperoxide: The role of the tert-butylperoxy radical
McLaughlin, Emily C.,Choi, Hojae,Wang, Kan,Chiou, Grace,Doyle, Michael P.
supporting information; experimental part, p. 730 - 738 (2009/07/04)
Dirhodium(II) caprolactamate exhibits optimal efficiency for the production of the tert-butylperoxy radical, which is a selective reagent for hydrogen atom abstraction. These oxidation reactions occur with aqueous tert-butyl hydroperoxide (TBHP) without rapid hydrolysis of the caprolactamate ligands on dirhodium. Allylic oxidations of enones yield the corresponding enedione in moderate to high yields, and applications include allylic oxidations of steroidal enones. Although methylene oxidation to a ketone is more effective, methyl oxidation to a carboxylic acid can also be achieved. The superior efficiency of dirhodium(II) caprolactamate as a catalyst for allylic oxidations by TBHP (mol % of catalyst, % conversion) is described in comparative studies with other metal catalysts that are also reported to be effective for allylic oxidations. That different catalysts produce essentially the same mixture of products with the same relative yields suggests that the catalyst is not involved in product-forming steps. Mechanistic implications arising from studies of allylic oxidation with enones provide new insights into factors that control product formation. A previously undisclosed disproportionation pathway, catalyzed by the tert-butoxy radical, of mixed peroxides for the formation of ketone products via allylic oxidation has been uncovered.
Allylic Oxidations Catalyzed by Dirhodium Catalysts under Aqueous Conditions
-
Page/Page column 16-18; 20, (2009/04/24)
The present invention relates to compositions and methods for achieving the efficient allylic oxidation of organic molecules, especially olefins and steroids, under aqueous conditions. The invention concerns the use of dirhodium (II,II) “paddlewheel complexes, and in particular, dirhodium carboximate and tert-butyl hydroperoxide as catalysts for the reaction. The use of aqueous conditions is particularly advantageous in the allylic oxidation of 7-keto steroids, which could not be effectively oxidized using anhydrous methods, and in extending allylic oxidation to enamides and enol ethers.
Catalysis of Ene Reactions by Lithium Perchlorate
Davies, Alwyn G.,Kinart, Wojciech J.
, p. 2281 - 2284 (2007/10/02)
The ene reaction of some allylic hydrocarbons, and the metallo-ene reaction of some allyltin compounds, with 1,3,4-triazoline-2,5-diones or with diethyl azodicarboxylate as enophiles, in diethyl ether are strongly catalysed by lithium perchlorate.Azobenzene, on the other hand, reacts slowly with alkyltin compounds, undergoing hydrostannation.The reaction of cholesterol or of tributylallyltin with singlet oxygen is subject to a smaller catalysis.
Iron-catalyzed Autoxidation of Liposomal Cholesterol
Muto, Toshiki,Tanaka, Jun,Miura, Toshiaki,Kimura, Michiya
, p. 1561 - 1566 (2007/10/02)
The autooxidation of cholesterol in a benzene solution of egg lecithin and Fe(acac)3, giving products variously oxygenated in the steroidal ring B, proceeded with consumption of the unsaturated long chain fatty acid moieties, particularly C18:2, in the lechitin molecule.The reaction showed a marked β-stereoselectivity of epoxidation and was inhibited by a radical scavenger (BHT).Cholesterol was highly susceptible to ferric iron-catalyzed autoxidation within liposomes prepared by using lechitin.The oxidative degradation of the unsaturated moieties, C18:1 and C18:2, in the lechitin led to allylic oxidation as well as the β-stereoselective epoxidation of cholesterol.A radical scavenger inhibited both the degradation of these moities and the oxygenation of cholesterol.The oxygenation was retarded in liposomes prepared by using saturated dipalmitoyl lecithin, and was dominated by allylic oxidation giving cholesteryl hydroperoxide as the main product.Cholesterol in the liposomes containing egg lecithin was, thus, assumed to be co-oxidized with the unsaturated fatty acid moieties by radical pathway, when the liposomes were autoxidized in the presence of ferric catalyst.Keywords - cholesterol; egg lecithin; liposome; liposomal cholesterol; autoxidation; stereoselective epoxidation; lipid peroxidation; co-oxidation; radical pathway; iron catalyst
